url_mappable.rb

url_mappable.rb

require 'open-uri'

module Concern
  def self.extended(base)
    base.instance_variable_set(:@__deps, [])
  end
  def included(base)
    if (deps = base.instance_variable_get(:@__deps))
      deps << self
    else
      @__deps.each {|dep| base.include(dep)}
      super
      base.class_eval(&@__block) unless @__block.nil?
    end
  end
  def injected(&block)
    @__block = block
  end
end

module Validatable
  extend Concern
  injected do
    def self.validate(attribute, &block)
      attr_accessor attribute unless method_defined?(attribute)
      orig = "#{attribute}_orig="
      alias_method orig, "#{attribute}="
      define_method("#{attribute}=") do |val|
        self.__send__(orig, val) if block.(val)
      end
    end
  end
end

module URLMappable
  extend Concern
  include Validatable
  injected do
    def self.url_map_for(attribute)
      storage = "#{attribute}_storage"
      assign_attr = "#{attribute}="
      attr_accessor storage
      define_method(assign_attr) do |url|
        self.__send__("#{storage}=", URI.open(url).string)
      end
      define_method(attribute) do
        self.__send__(storage)
      end
      validate attribute do |val|
        begin
          res = URI.parse(val)
          res.is_a? URI::HTTP
        rescue URI::InvalidURIError
          nil
        end
      end
    end    
  end
end

class X
  include URLMappable
  url_map_for :url
end

p X.new.tap {|x| x.url = 'http://ipcheck.com/' }.url
p X.new.tap {|x| x.url = 'aa' }.url